Differential Uplift and Fragmentation of Upper Yangtze Basin in Cenozoic

Jiang Lei; Deng Bin; Liu Shugen; Wang Zijian; Zhou Zheng; Luo Qiang; He Yu; Lai Dong

Abstract：The Meso-Cenozoic Upper Yangtze continental basin is not only the core tectonic unit of the South China continent, but also a natural laboratory for the study of continental tectonics and basin genetic evolution.Based on LA-ICP-MS apatite FT-U/Pb double dating and thermal evolution history simulation of 6 samples in the Cretaceous stratigraphic Section of Chuxiong basin and Sichuan basin,this paper reveals the differential uplift and denudation and differentiation process of the Upper Yan-gtze basin.The AFT(apatite fission track)ages and track length of Jiangdihe Formation in the Yijiu Section of Dayao County in Chuxiong basin are dominated with 43.2—33.9 Ma and 10.06—11.30 μm,respectively.The thermal models suggest a rapid cooling occurred in Miocene with rates of 3—5 ℃/Ma.Whilst the AFT ages and track length in the Liujia Section of Yibin County in Sichuan basin are dominated with 128.0—95.2 Ma and 10.2—11.7μm,as a result of partial reset.Furthermore,the apatite U-Pb ages are consistent between the Yijiu and Liujia sections,characterized with peak-ages of 2 100—1 700 Ma,820—700 Ma,500—400 Ma,and 250—170 Ma,which indicates the Upper Yangtze basin had provenances from the Songpan-Ganzi flysch,Yidun arc,Kangdian paleo-uplift and Qinling orogen in Late Cretaceous.In particular,the contrast of apatite FT-U/Pb reveals that a few of apatite minerals from Sanhe-Gaokanba Formation stemmed from a first-cycle deposit of provenance with rapid cooling of granites during Late Triassic to Cretaceous.In the end,the Upper Yangtze basin has been dispersed and frag-mented with a rapid cooling and uplift in Miocene,and then forms the current basin framework,as a result of southeastward growth of Tibetan plateau.